I went ahead and purchased a Komfort Kollar, and will try it late next week on a late-night flight from SEA to FAI. It has a small, hard-to-inflate valve, which I guess ensures that very few will have the endurance to blow it up to explosive dimensions.
KK's come in three sizes, and since my neck is 16" I got the medium (14 - 16") size. This may or may not have been a wise decision, as the kollar is almost too small for komfort.
The KK, like its competitors, inflates all the way around your neck. This pushes your head forward if you are seated vertically. I imagine that a collar that inflated only in the front, to hold up the neck, would be better.
I've tested putting a nylon strap around the back of my seat and over my forehead (quite a sight!), to hold my head vertically. The strap had to fit over the closed tray table of the person behind me, which did not seem like a good idea.
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Middle_Seat